Spring clips for closing bags, which are sometimes referred to in commerce as “chip clips” in view of their widespread use for closing bags of potato crisps and the like, are exemplified in U.S. Pat. No. 5,802,677 Dorman et al. Such clips comprise a pair of jaws enlarged at one end to provide a bag engaging portion, and having at the opposed end an actuating portion, and a fulcrum intermediate the ends. A steel spring serves to retain the two jaws together in working relationship, and bias the bag engaging portions together.
It would be desirable to form such a clip entirely from thermoplastic material, so as to avoid rusting to which the steel spring is susceptible, particularly where this can be accompanied by economies in manufacture. Moreover, spring clips (which term is intended to include both clamping and dilating devices unless the context clearly is intended to refer to one or other types of clip) that are devoid of any metal component may be preferable for medical and other uses.
Spring clips utilizing plastic springs are described in the prior art. In U.S. Pat. No. 4,840,341 (HASEGAWA) there is disclosed a plastic clip comprising a pair of jaws and a fulcrum assembly comprising an elongated socket into which an elongated knuckle is snap-fitted, and a tongue which projects from one of the jaws to engage a shallow arcuate groove in the opposing jaw. As the clip is actuated by manual pressure to open the work engaging portions of the clip, the tongue is progressively deflected by the groove. This action increases the area of contact between the tongue and the groove, while simultaneously increasing the contact pressure therebetween. This type of spring is relatively inefficient.
In U.S. Pat. No. 5,361,463 (REVIS) and also related U.S. Pat. No. 5,452,500, there is describe a plastics spring clip which is unitarily molded, and which utilizes a folded plastic strip to bias the jaws of the clip closed, thereby avoiding the frictional engagement of the parts. However, the materials usage for the manufacture of this clip is relatively high, and maybe prohibitively expensive for a simple clip. Also, a single plastic leaf spring with a U-profile will exert a relatively weak biasing force.
In the above snap-together fulcrum assemblies, there remains a possibility of the assembly peeling apart. It would be desirable to provide in plastic spring clips utilizing a snap together fulcrum assembly a means for positively locking the assembly so as to preclude its coming apart.
It is an object of this invention to provide spring clips and the like which may be molded from a plastic material and which may have excellent spring characteristics.
It is another object of this invention to provide spring clips and the like that are economic in materials usage and that are easily assembled.
It is yet another object of this invention to provide in plastic snap-together clip a fulcrum assembly that may readily be locked so as not to be subject to unintentional dis-assembly.